Math Problem Statement

Find the p (∈ ℝ) values for which the following series is convergent: ∑ (n=1 to ∞) [(n^(1/3) + 1)^p] / [(n^(7/3) + n^(5/2) + 1)^(13/11)], where p > 0.

Solution

To determine the values of p>0p > 0 for which the given series converges, we analyze the series:

n=1(n1/3+1)p(n7/3+n5/2+1)13/11.\sum_{n=1}^\infty \frac{\left( n^{1/3} + 1 \right)^p}{\left( n^{7/3} + n^{5/2} + 1 \right)^{13/11}}.

Step-by-Step Analysis

  1. Asymptotic Behavior:

    • For large nn, the dominant term in n1/3+1n^{1/3} + 1 is n1/3n^{1/3}, and in n7/3+n5/2+1n^{7/3} + n^{5/2} + 1, the dominant term is n7/3n^{7/3}.

    • Therefore, the series asymptotically behaves as: n=1(n1/3)p(n7/3)13/11.\sum_{n=1}^\infty \frac{\left( n^{1/3} \right)^p}{\left( n^{7/3} \right)^{13/11}}.

      Simplifying: n=1np/3n(7/3)(13/11)=n=11nα,\sum_{n=1}^\infty \frac{n^{p/3}}{n^{(7/3) \cdot (13/11)}} = \sum_{n=1}^\infty \frac{1}{n^{\alpha}}, where: α=731311p3.\alpha = \frac{7}{3} \cdot \frac{13}{11} - \frac{p}{3}.

  2. Convergence Criterion:

    • The series n=11nα\sum_{n=1}^\infty \frac{1}{n^\alpha} converges if and only if α>1\alpha > 1.
    • Substituting α=731311p3\alpha = \frac{7}{3} \cdot \frac{13}{11} - \frac{p}{3}: 731311p3>1.\frac{7}{3} \cdot \frac{13}{11} - \frac{p}{3} > 1.
  3. Simplify the Inequality:

    • Compute 731311\frac{7}{3} \cdot \frac{13}{11}: 713311=9133.\frac{7 \cdot 13}{3 \cdot 11} = \frac{91}{33}.

      • The inequality becomes: 9133p3>1.\frac{91}{33} - \frac{p}{3} > 1.
    • Subtract 11 from both sides: 91331>p3.\frac{91}{33} - 1 > \frac{p}{3}.

    • Simplify 91331=91333333=5833\frac{91}{33} - 1 = \frac{91}{33} - \frac{33}{33} = \frac{58}{33}: 5833>p3.\frac{58}{33} > \frac{p}{3}.

    • Multiply through by 33 to isolate pp: p<35833=17433.p < \frac{3 \cdot 58}{33} = \frac{174}{33}.

  4. Result:

    • The series converges if 0<p<174330 < p < \frac{174}{33}, or equivalently: 0<p<5811.0 < p < \frac{58}{11}.

Would you like further clarifications or have specific questions about the steps?

Related Questions:

  1. What is the general criterion for the convergence of a pp-series?
  2. How does the dominant term affect the convergence of series?
  3. Can we use comparison tests to verify the result?
  4. How do fractional exponents impact series convergence?
  5. What happens when p>5811p > \frac{58}{11} or p=5811p = \frac{58}{11}?

Tip:

When determining the convergence of a series, always simplify the dominant terms for large nn to identify the growth rate accurately.

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Math Problem Analysis

Mathematical Concepts

Series Convergence
Asymptotic Analysis
Power Series
Comparison Test

Formulas

Asymptotic behavior for large n: n^(1/3) + 1 ~ n^(1/3), n^(7/3) + n^(5/2) + 1 ~ n^(7/3)
General series convergence: ∑ (1/n^α) converges if and only if α > 1

Theorems

p-Series Test
Comparison Test

Suitable Grade Level

Undergraduate Mathematics